There are various test items in a test for the mobile terminal. Among them, an output power control function is an important test item.
In a system in which one base station communicates with a plurality of mobile terminals at the same time, it is necessary to appropriately set the output power of the mobile terminals. Therefore, when the mobile terminal is connected to the base station, the mobile terminal transmits the type of random access preamble instructed by the base station with a relatively low output power through a specific channel, specifies, for example, uplink (UL) or downlink (DL) timing on the basis of response information to the type of random access preamble, which is transmitted from the base station, and changes to a communication state.
In the random access process, when there is no response from the base station, the mobile terminal repeatedly performs a process of increasing the output power by a predetermined value and transmitting the random access preamble again.
When testing the output power increase function, the test device does not deliberately respond to a signal transmitted from the mobile terminal and monitors the level of the received signal to grasp how the output power of the mobile terminal increases sequentially.
During the test, the mobile terminal sequentially increases an output power designation value for designating the output power therein by a predetermined value. However, there are two types of mobile terminals, one of which continuously increases the output power designation value in the mobile terminal even after the output power of the mobile terminal is saturated and updates the output power designation value and the other of which does not perform the increase and update process, when a state in which a response is not transmitted from the base station is maintained. One of the important tests is to specify the type of mobile terminal to be tested.
As a method for confirming this, a method is considered which transmits, to a mobile terminal, an output power reduction instruction to reduce the output power of the mobile terminal by a predetermined value ΔQ (for example, 1 dB) and to transmit data, using a closed loop power control, in a designation value saturation level excess state in which the output power of the mobile terminal reaches a saturation level and an output power designation value for designating the output power is predicted to be within a predetermined range that is greater than the saturation level.
When receiving the output power reduction instruction, the mobile terminal reduces the output power designation value therein by the predetermined value ΔQ and transmits, for example, data through a predetermined channel. The test device receives the data and measures the level of the data.
In the case of the mobile terminal in which the output power designation value is not increased and not updated after the output power is saturated, after the output power reduction instruction is received, the output power is reduced from the saturation level by the predetermined value ΔQ. In contrast, in the case of the mobile terminal in which the output power designation value is increased and updated after the output power is saturated, even when the output power designation value is reduced by the predetermined value ΔQ after the output power reduction instruction is received, the output power is not changed from the saturation level or it is not reduced by the predetermined value ΔQ.
Therefore, if the reception level of the signal from the mobile terminal after the output power reduction instruction is given is less than the reception level when the output power is saturated by the predetermined value ΔQ, the test device can specify the mobile terminal as a type which quickly responds to the output power reduction instruction. If the reception level is hardly changed from the reception level when the output power is saturated or is not reduced by the predetermined value ΔQ, the test device can specify the mobile terminal as a type which does not quickly respond to the output power reduction instruction.
The following Patent Document 1 discloses an example of the structure of a device which performs an output power control test for a mobile terminal.